Odds are if you find yourself traveling again and again with the same airline, you're going to want to apply for one of their credit cards. Most co-branded airline credit cards take a similar form- bonus points on flight purchases, priority boarding, and a free checked bag.

Sound familiar? Even within this common mold, some airline credit cards really stand out and offer perks that apply well beyond travel on their own flights. So today let's take a look at the best airline credit cards of 2018.

Now, in addition to earning 2 miles per dollar on AA purchases, you'll also earn 2x at restaurants and gas stations. You can also earn a $100 flight discount if you spend $20,000 on the card in one membership year and renew your account. To top it off the card has a limited time elevated bonus of 60,000 miles after spending $3,000 in the first 3 months.

One of the most common complaints I hear about airline miles is that people have trouble using them, they can never find award space. That's not a problem you'll have with Southwest, as the cost of an award ticket is directly tied to the cash price. This means that you'll never score an incredibly high value redemption with Rapid Rewards points, but as long as Southwest is still selling seats on the flight you'll always be able to use your points to book them.

With the Rapid Rewards Plus card you'll earn 2 points per dollar on Southwest purchases and 1 point everywhere else, as well as a 3,000 point anniversary bonus when you renew your account. Because of the revenue based award chart I value Southwest points at 1.5 cents each which means the anniversary bonus almost covers the entire $69 annual fee.

Possibly the best thing about this card is that the points you earn count towards the Southwest Companion Pass. Since hotel points transfers no longer count, Southwest credit cards are now one of the best and easiest ways to earn a year (or two) of free flights for your companion. Just remember you can't apply for the Rapid Rewards Plus and Premier cards anymore, you're now limited to one personal Southwest card per person.

Whether Alaska is your go-to airline or you've never set foot on one of their flights, the Mileage Plan miles you earn with the Alaska Airlines Visa Signature card are some of the most valuable ones out there. I consider Alaska miles to be the most valuable of any airline, and they're even worth as much to me as flexible transferable Amex Membership Rewards points. That's because even though Alaska isn't part of a major alliance, it partners with 5-star airlines like Cathay Pacific and JAL with very reasonable redemption rates.

If you do fly Alaska even once or twice a year, this card belong in your wallet. Between the free checked bag (for you and up to six companions) and the incredibly flexible $99 companion fare, it's easy to earn back the $75 annual fee and much more.

Between United and it's many Star Alliance partners, the miles you earn from the MileagePlus Explorer card can help you get nearly anywhere in the world. United cardholders also get one perk that I wish other airlines would offer as well: access to additional award space. These seats are a different fare code than United's normal award space and can give you more options to redeem your miles.

United is also the only major US airline to offer any kind of lounge access on its entry-level credit card. MileagePlus cardholders get 2 United Club passes a year when you renew your account. If you travel a lot with United you could also get the United MileagePlus Club Card which comes with a full United Club membership. That card has a $450 annual fee and is currently offering a sign-up bonus of 50,000 miles after spending $3,000 in 3 months.

Beginning June 1st, the MileagePlus card will also offer 2 points per dollar at restaurants and hotels, a fee credit for Global Entry or TSA PreCheck and 25% off in-flight purchases all for the reasonable annual fee of $95.

With a $450 annual fee, the Delta Reserve credit card is the most expensive of the 3 Delta co-branded cards that Amex issues but it does come with some impressive perks. Frequent travelers will enjoy the complimentary Sky Club access when traveling on Delta, while anyone looking to qualify for elite status will enjoy the opportunity to earn bonus MQMs. In addition to the sign-up bonus of 40,000 miles and 10,000 MQMs after spending $3,000 in the first 3 months, cardholders will earn 15,000 MQMs when they spend $30,000 in a year and another 15,000 if they spend $60,000. If you're going for Delta elite status they will waive the MQD requirement up to Platinum if you spend $25,000 on any of their co-branded cards, but they recently increased the waiver for Diamond up to $250,000. The card also includes a companion certificate each year on your account anniversary, a free checked bag, and 2 miles per dollar on Delta purchases.

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*The credit card offers that appear in this article are from credit card companies from which Forbes and The Points Guy receive compensation. This compensation may impact how and where products appear (including, for example, the order in which they appear). This article does not include all credit card companies or all available credit card products.

Brian Kelly is the founder and CEO of The Points Guy (TPG), the preeminent voice in the industry of points, miles and everything travel-related. Kelly launched TPG in 2010 during his time as a Wall Street road warrior, where he developed his keen sense for maximizing travel...